As radio circuits become more complex and also are designed to work at still higher frequencies, the elements tend to consume more power. Frequency dividers are important elements of radio circuits, and are for example used for synthesizing signals of desired frequency and phase. For example, multi-band radio circuits rely on the ability to generate signals at different controllable frequencies. Another example is application of beamforming where a plurality of antennas is fed by signals with a controlled phase such that the arrangement of the plurality of antennas provides a desired directional characteristic.
It is foreseen that cellular systems may use millimeter waves. The frequencies may in such cases range from about 15 to 60 GHz. In order to use the system outdoors, a longer cyclic prefix may be used compared with 60 GHz indoor systems. For this, a closer sub-carrier spacing in the OFDM modulation may be advantageous, however posing stringent phase noise requirements. At the same time beamforming is advantageously supported to increase the range and capacity of the system. A large number of antenna elements are then used. The signal at each element will have an individual phase shift which controls the beam direction. One key implementation alternative is to impose phase shifts in the local oscillator signal. The local oscillator frequency is in such cases preferably made programmable to be able to operate on different channels and in different bands.
An implementation of the local oscillator generation circuitry beneficially strives towards achieving low phase noise, individually programmable phase, programmable frequency, and/or distributing the signals to all transceivers in a beamforming system, all without consuming excessive power.
It is therefore a desire to provide an approach for an electronic circuit providing one or more of the above mentioned desired features at a moderate power consumption.